Planck intermediate results Aller, H. D.; Aumont, J.; Baccigalupi, C. ...
Astronomy and astrophysics (Berlin),
2016, Letnik:
596
Journal Article
Recenzirano
Continuum spectra covering centimetre to submillimetre wavelengths are presented for a northern sample of 104 extragalactic radio sources, mainly active galactic nuclei, based on four-epoch Planck ...data. The nine Planck frequencies, from 30 to 857 GHz, are complemented by a set of simultaneous ground-based radio observations between 1.1 and 37 GHz. The single-survey Planck data confirm that the flattest high-frequency radio spectral indices are close to zero, indicating that the original accelerated electron energy spectrum is much harder than commonly thought, with power-law index around 1.5 instead of the canonical 2.5. The radio spectra peak at high frequencies and exhibit a variety of shapes. For a small set of low-z sources, we find a spectral upturn at high frequencies, indicating the presence of intrinsic cold dust. Variability can generally be approximated by achromatic variations, while sources with clear signatures of evolving shocks appear to be limited to the strongest outbursts.
Planck intermediate results Arnaud, M.; Aumont, J.; Baccigalupi, C. ...
Astronomy and astrophysics (Berlin),
2016, Letnik:
596
Journal Article
Recenzirano
The Planck mission, thanks to its large frequency range and all-sky coverage, has a unique potential for systematically detecting the brightest, and rarest, submillimetre sources on the sky, ...including distant objects in the high-redshift Universe traced by their dust emission. A novel method, based on a component-separation procedure using a combination of Planck and IRAS data, has been validated and characterized on numerous simulations, and applied to select the most luminous cold submillimetre sources with spectral energy distributions peaking between 353 and 857 GHz at 5′ resolution. A total of 2151 Planck high-z source candidates (the PHZ) have been detected in the cleanest 26% of the sky, with flux density at 545 GHz above 500 mJy. Embedded in the cosmic infrared background close to the confusion limit, these high-z candidates exhibit colder colours than their surroundings, consistent with redshifts z > 2, assuming a dust temperature of Txgal = 35 K and a spectral index of βxgal = 1.5. Exhibiting extremely high luminosities, larger than 1014L⊙, the PHZ objects may be made of multiple galaxies or clumps at high redshift, as suggested by a first statistical analysis based on a comparison with number count models. Furthermore, first follow-up observations obtained from optical to submillimetre wavelengths, which can be found in companion papers, have confirmed that this list consists of two distinct populations. A small fraction (around 3%) of the sources have been identified as strongly gravitationally lensed star-forming galaxies at redshift 2 to 4, while the vast majority of the PHZ sources appear as overdensities of dusty star-forming galaxies, having colours consistent with being at z > 2, and may be considered as proto-cluster candidates. The PHZ provides an original sample, which is complementary to the Planck Sunyaev-Zeldovich Catalogue (PSZ2); by extending the population of virialized massive galaxy clusters detected below z < 1.5 through their SZ signal to a population of sources at z > 1.5, the PHZ may contain the progenitors of today’s clusters. Hence the Planck list of high-redshift source candidates opens a new window on the study of the early stages of structure formation, particularly understanding the intensively star-forming phase at high-z.
Planck intermediate results Ashdown, M.; Atrio-Barandela, F.; Aumont, J. ...
Astronomy and astrophysics (Berlin),
02/2016, Letnik:
586
Journal Article
Recenzirano
The all-sky Planck survey in 9 frequency bands was used to search for emission from all 274 known Galactic supernova remnants. Of these, 16 were detected in at least two Planck frequencies. The ...radio-through-microwave spectral energy distributions were compiled to determine the mechanism for microwave emission. In only one case, IC 443, is there high-frequency emission clearly from dust associated with the supernova remnant. In all cases, the low-frequency emission is from synchrotron radiation. As predicted for a population of relativistic particles with energy distribution that extends continuously to high energies, a single power law is evident for many sources, including the Crab and PKS 1209-51/52. A decrease in flux density relative to the extrapolation of radio emission is evident in several sources. Their spectral energy distributions can be approximated as broken power laws, Sν ∝ ν−α, with the spectral index, α, increasing by 0.5–1 above a break frequency in the range 10–60 GHz. The break could be due to synchrotron losses.
Planck intermediate results Ashdown, M.; Aumont, J.; Baccigalupi, C. ...
Astronomy and astrophysics (Berlin),
2016, Letnik:
596
Journal Article
Recenzirano
The secondary cosmic microwave background (CMB) B-modes stem from the post-decoupling distortion of the polarization E-modes due to the gravitational lensing effect of large-scale structures. These ...lensing-induced B-modes constitute both a valuable probe of the dark matter distribution and an important contaminant for the extraction of the primary CMB B-modes from inflation. Planck provides accurate nearly all-sky measurements of both the polarization E-modes and the integrated mass distribution via the reconstruction of the CMB lensing potential. By combining these two data products, we have produced an all-sky template map of the lensing-induced B-modes using a real-space algorithm that minimizes the impact of sky masks. The cross-correlation of this template with an observed (primordial and secondary) B-mode map can be used to measure the lensing B-mode power spectrum at multipoles up to 2000. In particular, when cross-correlating with the B-mode contribution directly derived from the Planck polarization maps, we obtain lensing-induced B-mode power spectrum measurement at a significance level of 12σ, which agrees with the theoretical expectation derived from the Planck best-fit Λ cold dark matter model. This unique nearly all-sky secondary B-mode template, which includes the lensing-induced information from intermediate to small (10 ≲ ℓ ≲ 1000) angular scales, is delivered as part of the Planck 2015 public data release. It will be particularly useful for experiments searching for primordial B-modes, such as BICEP2/Keck Array or LiteBIRD, since it will enable an estimate to be made of the lensing-induced contribution to the measured total CMB B-modes.
Planck intermediate results Aghanim, N.; Arnaud, M.; Baccigalupi, C. ...
Astronomy and astrophysics (Berlin),
10/2015, Letnik:
582
Journal Article
Recenzirano
We have used the Planck all-sky submillimetre and millimetre maps to search for rare sources distinguished by extreme brightness, a few hundred millijanskies, and their potential for being situated ...at high redshift. These “cold” Planck sources, selected using the High Frequency Instrument (HFI) directly from the maps and from the Planck Catalogue of Compact Sources (PCCS), all satisfy the criterion of having their rest-frame far-infrared peak redshifted to the frequency range 353–857 GHz. This colour-selection favours galaxies in the redshift range z = 2–4, which we consider as cold peaks in the cosmic infrared background. With a \hbox{$4\farcm5$}4 .́ 5 beam at the four highest frequencies, our sample is expected to include overdensities of galaxies in groups or clusters, lensed galaxies, and chance line-of-sight projections. We perform a dedicated Herschel-SPIRE follow-up of 234 such Planck targets, finding a significant excess of red 350 and 500μm sources, in comparison to reference SPIRE fields. About 94% of the SPIRE sources in the Planck fields are consistent with being overdensities of galaxies peaking at 350μm, with 3% peaking at 500μm, and none peaking at 250μm. About 3% are candidate lensed systems, all 12 of which have secure spectroscopic confirmations, placing them at redshifts z> 2.2. Only four targets are Galactic cirrus, yielding a success rate in our search strategy for identifying extragalactic sources within the Planck beam of better than 98%. The galaxy overdensities are detected with high significance, half of the sample showing statistical significance above 10σ. The SPIRE photometric redshifts of galaxies in overdensities suggest a peak at z ≃ 2, assuming a single common dust temperature for the sources of Td = 35 K. Under this assumption, we derive an infrared (IR) luminosity for each SPIRE source of about 4 × 1012L⊙, yielding star formation rates of typically 700 M⊙ yr-1. If the observed overdensities are actual gravitationally-bound structures, the total IR luminosity of all their SPIRE-detected sources peaks at 4 × 1013L⊙, leading to total star formation rates of perhaps 7 × 103M⊙ yr-1 per overdensity. Taken together, these sources show the signatures of high-z (z> 2) protoclusters of intensively star-forming galaxies. All these observations confirm the uniqueness of our sample compared to reference samples and demonstrate the ability of the all-skyPlanck-HFI cold sources to select populations of cosmological and astrophysical interest for structure formation studies.
A steady-state two-dimensional model of the outermost region of a spiral galaxy is presented. The magnetic field, which is able to explain the flat rotation curve, is calculated, without the ...existence of any kind of dark matter. The vertical and radial distributions of the density are calculated, as well as the radial and vertical velocities. The magnetic field strength is noticeably constant in the peripheral disc, at about 7 × 10–7 gauss, much more moderate than that obtained in our previous model (Battaner et al.). The vertical velocities are driven by Parker’s instabilities and induce a moderate escape of gas of about 0.1 M⊙ yr–1 which prevents excessive flaring.
Planck intermediate results Aghanim, N.; Arnaud, M.; Aumont, J. ...
Astronomy and astrophysics (Berlin),
08/2015, Letnik:
580
Journal Article
Recenzirano
Any variation in the fundamental physical constants, more particularly in the fine structure constant, α, or in the mass of the electron, me, affects the recombination history of the Universe and ...cause an imprint on the cosmic microwave background angular power spectra. We show that the Planck data allow one to improve the constraint on the time variation of the fine structure constant at redshift z ~ 103 by about a factor of 5 compared to WMAP data, as well as to break the degeneracy with the Hubble constant, H0. In addition to α, we can set a constraint on the variation in the mass of the electron, me, and in the simultaneous variation of the two constants. We examine in detail the degeneracies between fundamental constants and the cosmological parameters, in order to compare the limits obtained from Planck and WMAP and to determine the constraining power gained by including other cosmological probes. We conclude that independent time variations of the fine structure constant and of the mass of the electron are constrained by Planck to Δα/α = (3.6 ± 3.7) × 10-3 and Δme/me = (4 ± 11) × 10-3 at the 68% confidence level. We also investigate the possibility of a spatial variation of the fine structure constant. The relative amplitude of a dipolar spatial variation in α (corresponding to a gradient across our Hubble volume) is constrained to be δα/α = (−2.4 ± 3.7) × 10-2.
Planck intermediate results Ashdown, M.; Battaner, E.; Benabed, K. ...
Astronomy and astrophysics (Berlin),
08/2015, Letnik:
580
Journal Article
Recenzirano
Planck data when combined with ancillary data provide a unique opportunity to separate the diffuse emission components of the inner Galaxy. The purpose of the paper is to elucidate the morphology of ...the various emission components in the strong star-formation region lying inside the solar radius and to clarify the relationship between the various components. The region of the Galactic plane covered is l = 300° → 0° → 60° wherestar-formation is highest and the emission is strong enough to make meaningful component separation. The latitude widths in this longitude range lie between 1° and 2°, which correspond to FWHM z-widths of 100−200 pc at a typical distance of 6 kpc. The four emission components studied here are synchrotron, free-free, anomalous microwave emission (AME), and thermal (vibrational) dust emission. These components are identified by constructing spectral energy distributions (SEDs) at positions along the Galactic plane using the wide frequency coverage of Planck (28.4−857 GHz) in combination with low-frequency radio data at 0.408−2.3 GHz plus WMAP data at 23−94 GHz, along with far-infrared (FIR) data from COBE-DIRBE and IRAS. The free-free component is determined from radio recombination line (RRL) data. AME is found to be comparable in brightness to the free-free emission on the Galactic plane in the frequency range 20−40 GHz with a width in latitude similar to that of the thermal dust; it comprises 45 ± 1% of the total 28.4 GHz emission in the longitude range l = 300° → 0° → 60°. The free-free component is the narrowest, reflecting the fact that it is produced by current star-formation as traced by the narrow distribution of OB stars. It is the dominant emission on the plane between 60 and 100 GHz. RRLs from this ionized gas are used to assess its distance, leading to a free-free z-width of FWHM ≈ 100 pc. The narrow synchrotron component has a low-frequency brightness spectral index βsynch ≈ −2.7 that is similar to the broad synchrotron component indicating that they are both populated by the cosmic ray electrons of the same spectral index. The width of this narrow synchrotron component is significantly larger than that of the other three components, suggesting that it is generated in an assembly of older supernova remnants that have expanded to sizes of order 150 pc in 3 × 105 yr; pulsars of a similar age have a similar spread in latitude. The thermal dust is identified in the SEDs with average parameters of Tdust = 20.4 ± 0.4 K, βFIR = 1.94 ± 0.03 (> 353 GHz), and βmm = 1.67 ± 0.02 (< 353 GHz). The latitude distributions of gamma-rays, CO, and the emission in high-frequency Planck bands have similar widths, showing that they are all indicators of the total gaseous matter on the plane in the inner Galaxy.
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